1. Field of the Invention
The present invention relates to a polishing apparatus and a polishing method, and more particularly to a polishing apparatus and a polishing method for polishing and planarizing a surface of a polishing object (substrate), such as a wafer, while preventing the formation of scratches on the surface of the polishing object, caused by a polishing liquid that has been scattered and dried.
The present invention also relates to a polishing apparatus, and more particularly to a polishing apparatus for polishing and planarizing a surface of a polishing object (substrate), such as a wafer, while preventing a polishing liquid from contaminating various covers and other parts disposed around a polishing table.
2. Description of the Related Art
A polishing apparatus for polishing a wafer surface generally includes a polishing table for supporting a polishing pad having a polishing surface, and a top ring (or a polishing head) for holding a wafer. While the polishing table and the top ring are moved relative to each other, the wafer, held by the top ring, is pressed against the polishing surface of the polishing pad at a predetermined pressure to come into sliding contact with the polishing surface. As a result, the wafer is polished to have a flat mirror surface. In the case of chemical mechanical polishing (CMP), a polishing liquid (or slurry) is supplied onto the polishing pad during polishing.
When the surface of the substrate, such as a wafer, is polished while the polishing liquid is supplied to the polishing pad, the polishing liquid is scattered around the polishing table. After the polishing of the substrate, a liquid (e.g., pure water) or a mixed fluid of a liquid (e.g., pure water) and a gas (e.g., nitrogen gas) is sprayed in a mist state from an atomizer to the polishing surface of the polishing pad to clean the polishing surface. During the cleaning of the polishing surface by means of the atomizer, the polishing liquid remaining on the polishing surface is also scattered around the polishing table. The scattered polishing liquid can be attached to and dried on various constituent parts disposed around the polishing table or on an inner surface of a chamber in which the polishing apparatus is housed. If the dried polishing liquid falls onto the polishing table, the fallen matters may cause a scratch on the substrate.
In general, various cleaning nozzles are disposed in predetermined positions in the polishing apparatus. A cleaning liquid is periodically emitted from the cleaning nozzles toward predetermined sites in the polishing apparatus in order to rinse off the polishing liquid that has been attached to the polishing table or the surfaces of constituent parts disposed around the polishing table. However, despite the rinsing with the cleaning liquid, some polishing liquid may remain and be dried on the surfaces of the constituent parts disposed around the polishing table. Once the polishing liquid is attached to and dried on the surfaces of the constituent parts, it is difficult to rinse off the dried polishing liquid with the cleaning liquid. Moreover, if the dried polishing liquid is deposited repeatedly, the dried polishing liquid may fall onto the polishing pad, thus causing a scratch on the substrate.
A top ring head cover that surrounds a top ring head having the top ring may be employed to protect the top ring head from the scattered polishing liquid. The polishing apparatus typically includes a dresser for dressing the polishing surface. A dressing head cover that surrounds a dressing head having the dresser may be employed to protect the dressing head from the scattered polishing liquid. Further, an atomizer cover that surrounds spray nozzle(s) of the atomizer may be employed to prevent dispersion of the mixed fluid or the polishing liquid that has bounced off the polishing pad.
The atomizer cover generally has a fairly complicated shape. As a result, a liquid containing the polishing liquid, which has bounced off the polishing pad, is likely to stay in the atomizer cover. In addition, since the atomizer cover has a number of corners where the liquid is likely to remain, it is generally difficult to clean an external surface of the atomizer cover with a cleaning liquid. If the liquid containing the polishing liquid is attached to and solidified on the atomizer cover, the solid matter may fall onto the polishing surface, thus contaminating the polishing surface.
It is difficult to completely prevent the scattered polishing liquid from flowing into the top ring head cover. Thus, the polishing liquid may enter the interior of the top ring head cover and stay there, thus contaminating the top ring head cover or the top ring head. Further, the polishing liquid may drop from the top ring head cover onto the polishing surface, thus contaminating the polishing surface.